As is known, today's passenger cars mount electronic circuits of the integrated kind which are designed to drive such electric loads as lights, electric motors, actuators, and the like, on voltage from a supply battery and through the car's own electric system.
The electric system distribution lines may be affected by sharp voltage fluctuations due to correspondingly sharp changes in the input current to electrical apparatus activated by the user, such as when turning on windshield wipers, air conditioners, or lights, and in relation to the line inductances.
Where overvoltages or undervoltages appear at the power supply, the integrated control circuits for the various electric loads may suffer damage.
To obviate this problem, the use of integrated circuits would be conceivable which can successfully withstand such voltage fluctuations; however, the engineering involved in the manufacture of these circuit types is a substantially expensive one, both in terms of the components and processing required.
Another prior approach consists of connecting, between the integrated circuit and ground, a device which provides protection against said overvoltages; but this also aggravates the manufacturing costs, as well as adding to the cost of assembling the electric system to a car.